cowboyeagle05 wrote:Also its a game of who gets their project built first. TXDOT will take into account the likelihood that DART will get D2 built before TXDOT gets funding for a highway rebuild.

Certain Parties were pushing for D2 to be subway in the vicinity of 345 so it would effectively poison the well against any tunnel/trench 345 alternatives, and an at-grade D2 in the vicinity of 345 would harm Certain Parties' plan for an at-grade boulevard to replace 345.

If I'm TxDOT, I'm doing my alternatives analysis independent of D2, and telling Certain Parties they're on the hook for any extra costs required as a result of their attempt to poison-pill the 345 alternatives they didn't want.

Alex Rodriguez wrote:This is a win for those of us that argue that you can't just remove I-345 without understanding the ramifications to the rest of the street/freeway system. Also that you can't remove I-345 without major upgrades to the rest of the street/freeway system, in advance of tear-down.

Literally no one thinks that should should tear down I-345 without studying its impact on the rest of the transportation system.

Regardless, this study has nothing to do with that. This is the economic development study. And A New Dallas (i.e. the org dedicated to making an I-345 teardown happen) is in full support of the postponement to include all the downtown-adjacent projects. TxDOT will be announcing later this month that it is funding a full planning and engineering study on I-345.

Also, you're aware that the I-30 reconstruction and Lowest Stemmons projects are about to get approval at the next TxDOT Commission meeting for $2 billion to build them, right? The imminent nature of these projects is why they were included in the modeling.

tanzoak wrote:Literally no one thinks that should should tear down I-345 without studying its impact on the rest of the transportation system.

This is false. There are a ton of people advocating this. Maybe not your group, but the old 50 page thread I'd say nearly half of them advocated "lets close the road and see what happens," or "just tear it down, people will figure it out/reroute."

The rest of it we discussed ad nauseum last month not going to get into it again. My position is clear just go reread the first 3 pages of this thread if you're interested

Alex Rodriguez wrote:This is false. There are a ton of people advocating this. Maybe not your group, but the old 50 page thread I'd say nearly half of them advocated "lets close the road and see what happens," or "just tear it down, people will figure it out/reroute."

Ok, well not doing traffic impact studies is not part of the possibility space, so you don't need to spend time arguing against that, just FYI.

Also, again, this economic development study is separate from the forthcoming traffic impact analysis.

So earlier in this thread, I said that a legitimate argument for skepticism of CityMAP findings is that the error ranges on these models can be quite large, but also that to the extent that the estimates are incorrect, a TxDOT study is more likely to produce estimates biased in favor needing more road capacity rather than the opposite.

Well.. Last week I talked to the guy who led the transportation assessment of the DD360 Plan. When they started with model validation of the NCTCOG model for the DD360 study area, they found that it was over-estimating trips on downtown streets by 50% (!!). That's.. terrible.*

They re-calibrated the model for use in DD360 forecasts to match real-world conditions downtown, but CityMAP (which was further along, and just a preliminary study), used the standard model, meaning that it significantly over-estimates congestion on city streets downtown. For those who don't remember, the main finding of CityMAP was that an I-345 removal wouldn't affect overall congestion much, but it would shift more of that congestion to city streets. If there's more excess capacity on downtown streets than what the unrefined NCTCOG model estimates, that's great news for an I-345 removal.

*While 50% error is awful, it's also the case that NCTCOG's focus is on getting highway flows right, not complex downtown local streets, and their base model is calibrated as such. I anticipate that for the next, more in-depth study, they'll use a modified, refined version of the model similar to the one used for DD360.

I wonder if the models provide any estimates on the number of people that would be killed by removing the highway?

For those going "WTF???", here are some reasons...

- Limited access highways are by far the safest roads. Move a couple hundred thousand cars a day onto surface streets and you will have many more accidents/injuries/fatalities.

- The proponents of eliminating the freeway say some users will use I-635 instead. From I-45/I-20 to US-75/I-635 is 22.5 miles. Taking I-635 around is 29.5 miles, roughly 1/3 longer. So figure 1/3 more accidents/injuries/fatalities.

- Have you ever heard of a pedestrian killed crossing I-345? Put all those cars on city streets with a dozen traffic lights and welcome to Frogger. Pedestrian/Auto incidents are already almost a daily event in the CBD.

Hannibal Lecter wrote:The proponents of eliminating the freeway say some users will use I-635 instead. From I-45/I-20 to US-75/I-635 is 22.5 miles. Taking I-635 around is 29.5 miles, roughly 1/3 longer. So figure 1/3 more accidents/injuries/fatalities.

Mathematically speaking, you've just suggested a perfect linear regression between accidents and extra miles driven. Where your model, using a dependent variable (accidents) and your independent variable (extra miles), would have a coefficient of determination (r^2) of 1. Essentially your model would predict for every extra miles driven you would expect 1 more accident. That is y = x. That's a very bold thing to say.

I can guarantee you a basic t-test would reject your Null Hypothesis (that your regression coefficient (slope) is +1) every single time. ..there just aren't many variables, in any field, that have a relationship as the one you suggested.

Disclaimer ...I don't work with traffic studies, but I do work with models.

In short, what you're suggesting is so unlikely (and I mean VERY unlikely) that some would deem it preposterous.

I trust the people in charge to build an unbiased model that is fair and is grounded in reality. Let's not fear monger over lives saved...

If lives is what we wanted to save, we would've done away with high speed limits on our streets/freeways long ago.

^ You have a point. Since there are historically more fatalities on I-635 per passenger mile than on I-345 then my back-of-envelope estimate probably understated the number of fatalities that would result.

Hannibal Lecter wrote:I wonder if the models provide any estimates on the number of people that would be killed by removing the highway?

For those going "WTF???", here are some reasons...

- Limited access highways are by far the safest roads. Move a couple hundred thousand cars a day onto surface streets and you will have many more accidents/injuries/fatalities.

- The proponents of eliminating the freeway say some users will use I-635 instead. From I-45/I-20 to US-75/I-635 is 22.5 miles. Taking I-635 around is 29.5 miles, roughly 1/3 longer. So figure 1/3 more accidents/injuries/fatalities.

- Have you ever heard of a pedestrian killed crossing I-345? Put all those cars on city streets with a dozen traffic lights and welcome to Frogger. Pedestrian/Auto incidents are already almost a daily event in the CBD.

CityMAP doesn't say anything about overall VMT one way or the other, and it's not so clear as you seem to think, because people adjust to change. While some trips that previously utilized 345 would still continue to be made, just longer, others would shift or be eliminated. Also, you're freeing up space for 10,000 or whatever lower-VMT residents as opposed to the counterfactual where those units are built further out, in places requiring more driving.

CityMAP does indicate that traffic will be transferred from highways to local streets, and you are correct that local streets have a higher fatality rate than freeways. A large part of that, though, is that most local arterials have high speeds of 35mph+. To the extent that local streets in the core have lower speeds, this impact is much reduced. It's tougher to die at 25mph.

Pedestrian safety would most likely not be negatively impacted. The things that are the primary influences on pedestrian safety are vehicle speeds, intersection design, and roadway widths, not traffic volumes. While higher speeds, unsafe intersection design, and wide roads are correlated with higher volumes, increasing volumes on a given roadway doesn't really reduce safety. The primary effect is to increase pedestrian compliance (you're less likely to jaywalk with a steady stream of cars than if they are sporadic). To the extent that increased local street congestion reduces speeds and increases pedestrian compliance, it may actually reduce pedestrian danger, provided intersection design is decent (which, given that all the local roads nearby would be rebuilt, you'd hope it would be). Sure, now there's an additional street to cross instead of an underpass, but I don't really see this being a big issue one way or the other.

tanzoak wrote:Also, you're freeing up space for 10,000 or whatever lower-VMT residents as opposed to the counterfactual where those units are built further out, in places requiring more driving.

CityMAP does indicate that traffic will be transferred from highways to local streets, and you are correct that local streets have a higher fatality rate than freeways. A large part of that, though, is that most local arterials have high speeds of 35mph+. To the extent that local streets in the core have lower speeds, this impact is much reduced.

Not only that, but ambient airborne particulate matter is a known risk factor for suicide, violent crime, and shortened life expectancy (I'm not citing journal articles here, so some may have controlled for socioeconomic status and some studies may not have). Maximum morbidity on all of those fronts is what we get when we channel traffic in the shortest available paths by crossing through the middle of town. Even without the lower-VMT feedback loop that tanzoak pointed out, it would already be a net reduction in mortality to move highway VMT out of the most populated areas of the Metroplex.

Any study that doesn't line out how much it would take to construct new access to replace the loss of the I-345 isn't worth a flip.

If you take out I-345, the only way from Central to I-45 going south would be to go Woodall Rogers, and take the 1 lane cloverleaf ramp onto Stemmons.

The Horseshoe wasn't built out for a future 2-3 lane flyover from Southbound Woodall to Southbound I-35E so that you could connect to 30 or 45. That's all new design and construction. Plus you have to remember that you haven't moved the Southbound Woodall to Northbound I-35E traffic, and you have haven't moved the Southbound Woodall to MHH Bridge/Trinity Groves traffic either. All you've done is add the ~200K cars that used to traverse I-345, and dumped it onto Woodall Rogers/I-35E (and the wonderful Downtown Dallas streets).

Good luck with that without reconstructing the interchange. Plus the interchange at Woodall/Central, plus the interchange at old I345/45. Plus the Canyon needs to be rebuilt, which already has an estimated cost of pushing $1 Billion.

Line it out and show everyone how much it will cost to build it out right, let everyone decide if its worth $5-6 Billion dollars to do this thing correctly, instead of living in a Millenial Fantasy World where all the people will just start riding their bikes to work. "Just tear it down, it won't impact anything" will be famous last words. The numbers do not work. Its math. You remove capacity for 200K cars = capacity for 200K cars is lost = where do 200K cars fit onto the grid now? Math. Dollars. I'm not necessarily opposed to tearing down I-345, let's just do it based on math and dollars and do it right.

Alex Rodriguez wrote:Any study that doesn't line out how much it would take to construct new access to replace the loss of the I-345 isn't worth a flip.

If you take out I-345, the only way from Central to I-45 going south would be to go Woodall Rogers, and take the 1 lane cloverleaf ramp onto Stemmons.

The Horseshoe wasn't built out for a future 2-3 lane flyover from Southbound Woodall to Southbound I-35E so that you could connect to 30 or 45. That's all new design and construction. Plus you have to remember that you haven't moved the Southbound Woodall to Northbound I-35E traffic, and you have haven't moved the Southbound Woodall to MHH Bridge/Trinity Groves traffic either. All you've done is add the ~200K cars that used to traverse I-345, and dumped it onto Woodall Rogers/I-35E (and the wonderful Downtown Dallas streets).

Good luck with that without reconstructing the interchange. Plus the interchange at Woodall/Central, plus the interchange at old I345/45. Plus the Canyon needs to be rebuilt, which already has an estimated cost of pushing $1 Billion.

Line it out and show everyone how much it will cost to build it out right, let everyone decide if its worth $5-6 Billion dollars to do this thing correctly, instead of living in a Millenial Fantasy World where all the people will just start riding their bikes to work. "Just tear it down, it won't impact anything" will be famous last words. The numbers do not work. Its math. You remove capacity for 200K cars = capacity for 200K cars is lost = where do 200K cars fit onto the grid now? Math. Dollars. I'm not necessarily opposed to tearing down I-345, let's just do it based on math and dollars and do it right.

Please

Dude just stop. Please. I work in the industry and do this type of analysis for a living. My firm did the DD360 modeling and transportation analysis and had some communication with the team doing CityMAP. I've also read what CityMAP did, which was laid out very clearly in the report. For the millionth time.. all of your claims about stuff they "didn't consider" or "didn't include" in the transportation analysis or cost estimates, they ABSOLUTELY DID. I get that you don't think it's a good idea. That's fine. But spreading misinformation on this forum is a completely inappropriate way to argue your opinion on what should be done.

Also, lol at the idea of these agencies and consulting firms being driven by some "Millenial Fantasy World." You do realize that the oldest millenials are like mid-30s, right? You really think that's who's PMing major projects like this? Newsflash, this is all dudes in their 50s and 60s. And they all drive to work. All of them. Even in the Bay Area, which given our awful traffic and excellent suburb-to-city transit is ridiculous, but it’s true.

I'm not clear what your insistence on "math" means, as all of these models are extremely math-intensive.. I get that you don't like their outputs, but the results aren't just something that someone makes up. It's from traffic modeling/simulation software that, while certainly not perfect, typically performs a lot better than layman gut instinct about traffic flows! Still, doubting the results is for sure perfectly legit, but the idea that they’re just ignoring basic math or whatever is just simply incorrect. You can argue against a tear-down and argue that traffic will be way worse than what this initial estimate is without making false claims about what they did.

Well let's see what the estimates are for redoing each component/option that will be required to replace part of the capacity. I lined them out in the previous post.

For instance, if a plan/option doesn't include the cost of redoing Woodall and Stemmons, so that all of Central Expressway isn't reduced to one cloverleaf ramp to get to I-45, then the plan is entirely worthless, because that is just common sense and math. You can spend 400 pages telling me how totally fine it will be if you leave that alone, and I can spend 30 seconds and tell you you are 100% wrong.

Alex Rodriguez wrote:Well let's see what the estimates are for redoing each component/option that will be required to replace part of the capacity. I lined them out in the previous post.

For instance, if a plan/option doesn't include the cost of redoing Woodall and Stemmons, so that all of Central Expressway isn't reduced to one cloverleaf ramp to get to I-45, then the plan is entirely worthless, because that is just common sense and math. You can spend 400 pages telling me how totally fine it will be if you leave that alone, and I can spend 30 seconds and tell you you are 100% wrong.

Canyon and Stemmons projects are getting built regardless of what's done with I-345. It makes no sense to include them as part of the I-345 project cost.

All of the stuff that you mentioned that directly interacts with I-345 is included in the I-345 project cost. They didn't break out the cost of each individual line item because that's irrelevant. All that is necessary at this point is what the project entails and what it costs. This isn't a construction order, it's a planning document.

tanzoak wrote: Canyon and Stemmons projects are getting built regardless of what's done with I-345. It makes no sense to include them as part of the I-345 project cost.

All of the stuff that you mentioned that directly interacts with I-345 is included in the I-345 project cost. They didn't break out the cost of each individual line item because that's irrelevant. All that is necessary at this point is what the project entails and what it costs. This isn't a construction order, it's a planning document.

We've covered all of this before.

Send me the link to the "Stemmons Project" that you are referring to where the Cloverleaf 1 lane ramp southbound is addressed. (Hint: Good Luck. If you answer "Lower Stemmons" you've answered incorrectly. Go to 0:33 of this youtube video to see that nothing is done with the interchange southbound between I-35E and WR. https://www.youtube.com/watch?v=KtXwJ6s-w8A )

When I get a quote for a Bathroom Remodel, it better be line itemed out and that is a 20K project or less. This is Billions of dollars and you are telling me that a line itemed proposal is "irrelevant." Welcome to government.

Alex Rodriguez wrote:Send me the link to the "Stemmons Project" that you are referring to where the Cloverleaf 1 lane ramp southbound is addressed. (Hint: Good Luck. If you answer "Lower Stemmons" you've answered incorrectly. Go to 0:33 of this youtube video to see that nothing is done with the interchange southbound between I-35E and WR. https://www.youtube.com/watch?v=KtXwJ6s-w8A )

When I get a quote for a Bathroom Remodel, it better be line itemed out and that is a 20K project or less. This is Billions of dollars and you are telling me that a line itemed proposal is "irrelevant." Welcome to government.

Ok, well if it's not in the Lowest Stemmons project, then it's not included. The resulting congestion numbers therefore include leaving that configuration as is. You don't "have to" do it with an I-345 teardown, as you're claiming. Maybe you think it would be a good idea to do it, and it sounds like it might reduce congestion. But considering that leaving the interchange as is results in limited systemwide congestion increases with a teardown (which is different from likely increased localized congestion at that particular location), I'm skeptical it would be worth the expense. Regardless, it's a separate project that would be analyzed on its own merits.

In your example, you're getting a bid. At that point, of course everything is line itemed out, as it would be done in more detail here. But we're not at that point yet. They've done it, of course, to get the rough estimate, but it's not included in the report because that level of granularity isn't relevant to a plan-level decision.

To go with a house example, it's like you have a beachfront property and have contacted a developer to get a sense of your options. The developer says, "Well, you could have a shack built for ~$100k, a normal house built for ~$350k, or a mansion built for ~$2m." You wouldn't snap back at the developer with "How can I possibly make this decision without knowing how much you're estimating the garage for the normal house would cost?!" You're trying to get a sense of rough costs and benefits at this point, and it's only after deciding the normal house makes the most sense for you do questions like "do I want to spend an extra $10k for the larger garage?" come into play.

"How can I possibly make this decision without knowing how much you're estimating the garage for the normal house would cost?!"

And if you want to argue about the unit cost of rebar or whatever like you do in your house bathroom remodel, the City Council produces those documents too as part of the Buy Board contract and then later approves them.

Has any of the studying told us who actually uses I-345? Surely we know how the trips sort out.... and really how many of those trips were supposed to redirect to any part of I-635? All the highways lead to downtown because that's the history of the roads, traffic using any combination of I35, I30/20, I345, SH75, Tollway to commute across the downtown is a recent thing, and how much of the micro-ring (Woodall Rodgers - I-345) is a two-generation response to suburbia that now needs a $2 billion correction?

I-345 exists as a reliever route for LBJ?!?!?! Ya, I think it kinda does.

I'm still okay keeping an elevated thru lanes connecting Central and I-45 --- only until I-45 is rebuilt braided into the I35/30 mixmaster. I used to think I liked that plan to reroute I-30 parallel to White Rock Creek the hooking up with I45 close to Rochester Park and both heading into the mixmaster, but I don't think I want the highway near the creek, I would rather have I30 trenched through East and South Dallas with I45 doubling down as road to Houston and levee support infrastructure.

City: "Sir, the cost to remove the street that runs along the front of your house and your driveway is $500,000."

Me: "Okay, well that's great, but how much is it going to cost to build me an alternate route to my house."

City: "Well sir, that's irrelevant. You can park your car down the street and ride a bike or walk to your house. Or you can buy a truck and drive on the muddy dirt road, you'll just have to figure it out. Maybe some day in the future we'll figure out how to replace the road"

tamtagon wrote:Has any of the studying told us who actually uses I-345? Surely we know how the trips sort out.... and really how many of those trips were supposed to redirect to any part of I-635? All the highways lead to downtown because that's the history of the roads, traffic using any combination of I35, I30/20, I345, SH75, Tollway to commute across the downtown is a recent thing, and how much of the micro-ring (Woodall Rodgers - I-345) is a two-generation response to suburbia that now needs a $2 billion correction?

I-345 exists as a reliever route for LBJ?!?!?! Ya, I think it kinda does.

I think there is some validity to the point that SOME traffic will be able to use 20/LBJ and route around downtown. What that SOME is, is point of disagreement, I don't anyone has any data that definitely states how many of the ~170K cars a day or whatever the number is right now, will go alternate route LBJ/20.

My point in this is that number is really irrelevant. The numbers that matter is 170K. You are removing 170K worth of capacity in already pretty much full freeway system in Downtown. Period end of story. So then, in order to actually do this right, you have to figure some reasonable accommodation for those 170K cars. How much capacity can you build and add to Good Latimer and Cesar Chavez? That's not going to be a whole lot, but it should be definable. And that should be a line item

XXX Millions to expand Good Latimer and Cesar Chavez to handle XXX additional cars per day.

That only gets you part of the way there. The rest of the line items should be:

* Reconstruct the Canyon - Thats $700 million right now* Reconstruct Woodall Rogers and I-35E - 1 single lane Southbound is NOT AN OPTION. 3 lanes of ramps from Woodall Rogers to I-35E. In each direction. XXXX Millions, and how much capacity does that add. * Reconstruct Central and Woodall Rogers - 3 lanes in each direction.

By removing I-345, you've basically made Central/Woodall/I-35 Stemmons one Freeway through Downtown, it needs to be constructed as a full 6 lane freeway all the way through or you might as well throw the entire tear down 400 page report with pretty color pictures in the trash. Either that or trench I-345.

tanzoak wrote:Ok, well if it's not in the Lowest Stemmons project, then it's not included. The resulting congestion numbers therefore include leaving that configuration as is. You don't "have to" do it with an I-345 teardown, as you're claiming. Maybe you think it would be a good idea to do it, and it sounds like it might reduce congestion. But considering that leaving the interchange as is results in limited systemwide congestion increases with a teardown (which is different from likely increased localized congestion at that particular location), I'm skeptical it would be worth the expense."

Lower and Lowest Stemmons were designed to alleviate the weaving and merging issues between Downtown and DNT. It is the building of collector/distributor roads to get traffic heading to Woodall, DNT, and North I-35E separated and flowing better. Lower Lowest Stemmons have ZERO elements designed to replace 170K worth of capacity lost by I-345.

Yeah, I'd say 100% of all southbound traffic on Central Expressway being forced to use Woodall Rogers, and then the probably 85-90% of that traffic that wants to get on I-35E South, or I-30 or I-45, yeah, its going to be a problem when all of that traffic has to use a 1 lane cloverleaf ramp. Yeah.

So far talking with my transportation and city planning friends outside of the forum I haven't seen a clear argument for why removing I-345 has to remain. Believe me, I get it removing a working highway does sound crazy and counter-intuitive. I have read the arguments back and forth here and while I see why people are afraid of such a change I am for it. Just the transportation math alone can definitely seem like an impossible situation and then when you add in first-hand accounts of seeing I-345 locked in traffic your first instinct would expand the freeway not demolish it.

The one thing I know for sure though is we were wrong about solutions to traffic in the 50's, 60's, and 70's. We still follow many of those methods because the public thinks those ideas are still true. Some planners as we know would turn some streets into wide sidewalks with bike lanes if they could but we all know the citizens would go ballistic even if it solved traffic overnight. Add another lane here widen this arterial there and bam traffic solved is what the last several decades of people have been told so they chant it back at the city council and planners who propose otherwise. It didn't work back then and still doesn't work today. Removing a freeway isn't a millennial rooted idea either it starts decades ago when planners, engineers, and let's face it local grass root leaders saw the social damage highways were producing and that it created drug addiction problem for expanding lanes that would only get larger with every expansion without much economic gain to pay for said expansion. It's not sustainable and I don't mean pollution either.

I can support its removal cause traffic in an urban area at rush hour will never go away and people who chase that pie in the sky idea that everyone can go home at 4-7 pm and get home in 15mins is delusional. It's the same crazy that thinks that everyone will be able to park in front of the front doors at every store they shop at. That person gets pissed when they have to park and walk through the lot so they circle through the parking lot over and over waiting for someone to leave. Let's be clear I am not advocating the removal of every individual car and highway, just that solutions that don't involve either one of those things have to be considered for their real advantages and potential to lessen the stress car-based cities are in.

Yeah, I'm kind of surprised by people who are engaged enough to visit/post on an urban affairs message board also claiming that it's basically impossible that this might work or that it will definitely cause a traffic nightmare. It's been done successfully in many places with freeways just as central as I-345 (see the Embarcadero in SF or the Cheonggyecheon in Seoul to name two). Context varies, and projects can be screwed up, of course, but like.. it's not some crazy harebrained scheme that's obviously a boneheaded idea. Highway tear-downs have a track record of success.

I've said it one hundred times. I am not opposed to tearing down I-345 it just needs to be done right. Replace as much of the capacity as you can by upgrading the rest of the system.

I'm surprised that people who advocate tear down are blind to what removing a 6-8 lane U.S. Interstate right in the middle of downtown will do the traffic situation for Dallas. And they are completely opposed to burying or trenching the road. If you want to do this right, then spend the money and do this right, don't half-a it.

As far as the pet Embarcadero analogy, I-345 handles 3 TIMES as much traffic as Embarcadero ever did: "Prior to the earthquake, the Embarcadero Freeway carried approximately 70,000 vehicles daily in the vicinity of the Ferry Building". Meanwhile, "The NCTCOG estimates there are more than 203,000 vehicles that travel I-345 each day."

By removing I-345 as a crosstown traffic route, an amazing amount of land becomes made available for development, much of which could be sequestered for civic parks and recreation. Allowing expansion to the Latin American Community Center that's so ridiculously under-developed every philanthropist in Dallas should be embarrassed (whatever, anyway). Infusing parks into this side of town should certainly should ease the sting of losing the Trinity River Tollway and the proposed floodplain Entertainment Extravaganza. A pedestrian and bike trail through here would be more popular than Katy Trail.

However, I do kinda like the physical separation the commuter short-cut provides between Downtown Dallas and Old East Dallas --- it's just not aesthetic.

Whatever is the outcome in the stay/go considerations, the primary mandate must be repairing the two surface street grids. Any sort of remnant I-345 access road capacity is transferred to Cesar Chavez-Pearl-Good-Latimer-Routh; CBD/OED extrance/exit to I-345 occurs at three spots: Ross, Carpenter Park Round-about, and I-30@Hall/Good-Latimer.

Should rebuilding the commuter short-cut turn out the answer, the finished product must use suspension bridge technology to provide for column-less street grids repair and 'covered' pedestrian/cyclist routes while pleasing the eye. It's like a garden wall -- if done right all the garden benefits, symbolic separation from one part of the garden from another.

Alex Rodriguez wrote:As far as the pet Embarcadero analogy, I-345 handles 3 TIMES as much traffic as Embarcadero ever did: "Prior to the earthquake, the Embarcadero Freeway carried approximately 70,000 vehicles daily in the vicinity of the Ferry Building". Meanwhile, "The NCTCOG estimates there are more than 203,000 vehicles that travel I-345 each day."

AADT from TxDOT in 2016 was 171k and 177k, and when combined with the parallel lanes below the elevated structure, the Embarcadero was 100k. It was also over capacity, suggesting the demand was even greater. The Cheonggyecheon was 169k, if you really need numbers that are super close. And if you're married to the total number of vehicles that use it at any point rather than AADTs, the Cheonggyecheon would have I-345 waaaay beat: it was 7 miles long. But all of this is picking nits.

An actually relevant argument against comparisons to these two examples, by the way, is that part of the reason why they ended up not causing carmaggedon is that a decent fraction of the vehicle trips just disappeared, part of which can be explained by shifting trips to alternative modes. That seems less likely in Dallas.

I'd also like point out that talking about how the alternative routes will handle 200k extra vehicles doesn't really represent the issue well. The only time any of this matters is during the peak hour, which is like 13,000 vehicles. (Or to be silly in the opposite direction, 200 per minute during the peak hour). It's still a legitimately large number, and there's a reason why a ton of study would go into it, but that gives a better sense of the scale of what we're concerned about than 200k.

As for a burial or below-grade option, a burial is just way too expensive, which is why TxDOT isn't even considering it. If the options were between a burial and the status quo, I would pick status quo, unfortunately, as the costs pretty clearly exceed the benefits in my opinion. As for sinking it below grade, the reason many oppose that option is that while a below-grade highway is better than an elevated one, it's not that much better. There's a little bit more land for development, it's a little bit less of a barrier, and you can put a deck park on a section of it. At the end of the day, you'd be spending a lot of money for something that makes traffic marginally worse and without a big transformational benefit. I don't really see the point. If it's below-grade or status quo, sure, go for it, but I don't really care that much.

tanzoak wrote:As for a burial or below-grade option, a burial is just way too expensive, which is why TxDOT isn't even considering it. If the options were between a burial and the status quo, I would pick status quo, unfortunately, as the costs pretty clearly exceed the benefits in my opinion.

What do you (and Alex) think about suspension-type overpass/bridges that would free up the street grids? Those are much more expensive, but supposed to last longer I think? and focusing entrance/exit ramps, using the Carpenter Park curve as the fulcrum of two segments.

I get that it's very clunky in the way that it's designed... But up until KWP was built, this was actually the least obstructive side of the mix master. I35E and I30 are easily more detrimental than I345 is. If they can't do a cut/cap option, than I think the best approach is to simplify the obnoxious ramps alongside this thing and call it a day. But simply removing the freeway and expecting traffic to 'go away' is overly optimistic. A 'boulivard' to absorb this traffic makes it more HOSTILE to pedestrians, not better. I don't see what a suspension bridge really accomplishes. My two cents anyway.

I get that it's very clunky in the way that it's designed... But up until KWP was built, this was actually the least obstructive side of the mix master. I35E and I30 are easily more detrimental than I345 is. If they can't do a cut/cap option, than I think the best approach is to simplify the obnoxious ramps alongside this thing and call it a day. But simply removing the freeway and expecting traffic to 'go away' is overly optimistic. A 'boulivard' to absorb this traffic makes it more HOSTILE to pedestrians, not better. I don't see what a suspension bridge really accomplishes. My two cents anyway.

What does your blvd look like? A properly designed one will include pedestrian amenities that will do more to encourage crossing than the current setup. If your idea of a BLVD is a slightly improved version of Northwest Hwy yeah, of course, I would agree. Some of the worlds best BLVD's balance both a heavy amount of automobile, bikes, and pedestrians. Keeping in mind this would be TXDOT designing the thing and not some famed transportation planner from the cities of Europe a high capacity blvd could be more friendly to pedestrians than Cedar Springs Rd is in its current form.

I-345 didn't haven't any significant effect on the street grid, because there wasn't much of a street grid there. Look at the old maps. For the most part I-345 follows the same rail line that that became North Central. Where the southern half I-345 is now used to be the railyards -- not streets. On the northern part only a couple very small streets were cut off.

The truth is that DART's Green Line did more damage to the street grid (and pedestrian access) than I-345 did.

tanzoak wrote:It's been done successfully in many places with freeways just as central as I-345 (see the Embarcadero in SF or the Cheonggyecheon in Seoul to name two). Context varies, and projects can be screwed up, of course, but like.. it's not some crazy harebrained scheme that's obviously a boneheaded idea. Highway tear-downs have a track record of success.

It's so handy when someone mentions the Embarcadero when discussing I-345. You know right away that they're just parroting stuff they've heard, and really don't know what they're talking about.

The Embarcadero was a glorified off ramp. It was planned as a major highway, but that was never built. The "Freeway" just dumped traffic onto city streets. Removing it simply meant the same cars hit the same streets a few blocks earlier.

We do have an equivalent of the Embarcadero Freeway here though, and it even went through a similar change. When headed south on US-75 stay to the left and take the Good-Latimer/Downtown exit. That last little stretch of the original North Central serves the same purpose the Embarcadero did, dumping traffic into the downtown street grid. It even got the same kind of haircut -- when DART built the Green Line they removed the overpass over Bryan Street and replace it with screwed up at-grade street and rail crossings, ending the "Freeway" a block earlier.

Hannibal Lecter wrote:It's so handy when someone mentions the Embarcadero when discussing I-345. You know right away that they're just parroting stuff they've heard, and really don't know what they're talking about.

I live in SF and work as a transportation engineer, so let’s hope that I have some sort of idea what I’m talking about.

The point wasn’t that the Embarcadero and I-345 are identical projects. It’s that’s it an example of a project where the lay public thought it was absolutely indispensable to avoid a congestion nightmare (removal got destroyed in a ballot prop in the 80s) despite traffic studies to the contrary. And lo and behold, when it came down, carmaggedon did not occur.

There are reasons why I-345 removal could go worse than the Embarcadero, but there are also reasons it could go better. You could use the Cheonggyecheon as the go-to example, but Americans generally connect better with American examples.

tanzoak wrote:As for a burial or below-grade option, a burial is just way too expensive, which is why TxDOT isn't even considering it. If the options were between a burial and the status quo, I would pick status quo, unfortunately, as the costs pretty clearly exceed the benefits in my opinion.

What do you (and Alex) think about suspension-type overpass/bridges that would free up the street grids? Those are much more expensive, but supposed to last longer I think? and focusing entrance/exit ramps, using the Carpenter Park curve as the fulcrum of two segments.

Hannibal Lecter wrote:It's so handy when someone mentions the Embarcadero when discussing I-345. You know right away that they're just parroting stuff they've heard, and really don't know what they're talking about.

I live in SF and work as a transportation engineer, so let’s hope that I have some sort of idea what I’m talking about.

The point wasn’t that the Embarcadero and I-345 are identical projects. It’s that’s it an example of a project where the lay public thought it was absolutely indispensable to avoid a congestion nightmare (removal got destroyed in a ballot prop in the 80s) despite traffic studies to the contrary. And lo and behold, when it came down, carmaggedon did not occur.

There are reasons why I-345 removal could go worse than the Embarcadero, but there are also reasons it could go better. You could use the Cheonggyecheon as the go-to example, but Americans generally connect better with American examples.

The reasons it could go worse are pretty obvious. I'd really like to see some reasons it could go better.

I get that it's very clunky in the way that it's designed... But up until KWP was built, this was actually the least obstructive side of the mix master. I35E and I30 are easily more detrimental than I345 is. If they can't do a cut/cap option, than I think the best approach is to simplify the obnoxious ramps alongside this thing and call it a day. But simply removing the freeway and expecting traffic to 'go away' is overly optimistic. A 'boulivard' to absorb this traffic makes it more HOSTILE to pedestrians, not better. I don't see what a suspension bridge really accomplishes. My two cents anyway.

The expectation isn't that the traffic just "goes away." Depending on the origin/destination, some trips would get diverted to local streets, some would get diverted to 635, some would get diverted to 35/Woodall, and some would not get made (either mode shift to transit, time shift outside of peak, shifting destination, or just not making the trip).

The expectation is that redistributing that traffic will not increase *congestion* too much.

Sure, if all 13,000 peak hour drivers just shifted to Woodall, as most opposition seems to think, that would increase congestion very much! But as it is, for all traffic traveling between south of 20 and north of 635, taking 635 is *already* a time-competitive option during the peak even with 345, it's just 7 miles longer. It's a pretty solid bet that most of that traffic will shift. This can actually reduce congestion because it reduces traffic on the highly-congested US-75, benefiting all of those travelers.

As for the shift to local roads, we focus on the boulevard, but it's about more than that. For example, I do/did a lot of traveling between north and east Dallas, and the travel time is the same whether I take I-30 to I-345 to 75 or local roads to 75. I usually take I-345 because I like going through downtown and prefer the highway. If I-345 was removed, I'd just take local roads to 75. On a broader scale, getting to/from I-45 via local roads at peak is already nearly time competitive even to/from close to 75 as far north as Mockingbird, and you'd see many of those trips shift to local roads instead of Woodall.

There are, of course, some O/D pairs where it would make sense to switch to Woodall, and that would certainly increase congestion there. The point is, though, that there are quite a bit fewer of those than you might think, and some of that increased congestion would likely be mitigated by reduced congestion on 75.

Tucy wrote:The reasons it could go worse are pretty obvious. I'd really like to see some reasons it could go better.

Basically, it comes down to the fact that there are a ton of different alternatives to using 345 (see above post) that involve shifting traffic to roadways that are less congested than 75, offering some large Braess' Paradox potential.* Compared to the Embarcadero, where the only alternative was to use city streets downtown and in the most densely-populated neighborhoods. Those city streets wouldn't have nearly the capacity to absorb as much traffic as Dallas' would (because already fairly congested at peak), which would be exacerbated by the fact that the impacts would be concentrated on a fewer number of streets due to the lower diversity of O/D pairs using the Embarcadero vs I-345.

*Braess' Paradox -- You're a driver with two options: a congested route with 100 other drivers, or route that takes you one minute longer but is totally empty (or at free-flow). Minimizing travel time for yourself, you choose the congested route, saving you 60 seconds. However, adding your car to the congested road results in 1 second of delay for each of the other 100 drivers, adding 100 extra seconds of travel time for a net increase of 40 seconds compared to the alternative. So the paradox is that, in a congested network, it's possible to actually improve travel times by eliminating network links (e.g. the link that allows the driver to access the congested road).

Are they though? Not really when you are on them they are so damn wide the arches kinda disappear and it feels like you are driving across an IKEA parking lot rather than a singular bridge. Hey, you can take some really cool pics from the river bottoms if you angle it right and cover up the 300 lanes of highway on the I-30 bridge though...

Conspiracies aside... This IS a really great idea. I always loved the dog park that had the overpass providing shading during the hot summer. Doing the same for soccer/other sports is great. Oh, and I don't buy the whole argument that having the park will prevent I 345 from ever coming down. Sheesh... if we ever can actually remove a freeway, the park will be easy as well... or, still useful (albeit with less shade).